Hermetically sealable mounting means



United States Patent 3,126,338 IETICALLY SEALABLE MOUNTING MEANS FUR ACENTRIFUGAL DRUM Peter Steinacker, Oelde, Westphalia, Germany, assignorto Westfalia Separator A.G., Oelde, Westphalia, Germany,

a German corporation Filed Nov. 29, 1960, Ser. No. 72,404 (Ilairnspriority, application Germany Nov. 30, 1959 7 Claims. (Cl. 233-23) Thepresent invention relates to a hermetically sealable mounting means fora centrifugal drum, and more particularly to such mounting means whichare oscillatingly displaceable together with the drum out of the normalposition thereof.

Hermetically sealed centrifugal drums, such as conventional separatordrums, usually have stationary inlet and outlet lines sealed withrespect to the rotating drum. Such constructions are generally used forthe separation of liquid mixtures, especially where the material to becentrifugally treated must not be exposed to contact with theatmosphere. Additionally, drum separators of the foregoing type areuseful for the centrifuging of solids from liquids advantageously, sincethe smooth passage into the drum of the material to be treated takesplace without the breaking up of solids suspended in the incomingliquid. For example, it may be desirable to clarify a liquid withrespect to suspended solids yet recover the solids portion of thematerial being treated substantially in its identical form and withoutthe same having been broken up by the centrifugal action. For the mostpart, however, since the clarifying capacity of a centrifugal drumdepends to a great degree upon the size of solids particles, a higherclarifying capacity of the drum separator is achieved when the breakingup of the solids particles is avoided. An efiicient clarification orseparation of solids particles from liquids as well as any separation ofa lighter from a heavier fraction of material, albeit a mixture of alighter liquid fraction and heavier liquid fraction, a lighter liquidfraction and heavier solid fraction, may accordingly take place. It isknown to employ solid packings or liquid seals for the sealing of thestationary inlet and outlet lines with respect to the rotatingcentrifugal drum parts, in order to achieve the passage into the drum ofmaterial to be treated and the passage from the drum of separatedfractions without leakage. However, the radial oscillations of thecentrifugal drum out of the normal position thereof act unfavorably onsuch packings or seals. Radial oscillations of the drum shaft out of thenormal axial position thereof often disadvantageously occur duringcentrifugal operations. Consequently, liquid packings or seals betweenthe stationary inlet and outlet lines and the corresponding drum partseither permit the leakage of liquid or the entry of air, while solidpackings or seals are subject to high wear and tear so as eventually topermit such leakage, entry of air, or remixing of the separatedcomponents.

Attempts have been made to decrease the rate of wear and tear on solidpackings and seals by constructing the same, for example, as sealingsleeves such that the point of connection will form an abutting edgedeveloped as a thin sealing lip. In such constructions either the sleevewill be stationary and the stationary lip will slidingly abut a rotatingconduit of the centrifuge, or else the sealing sleeve and lip willrotate with the centrifuge and will slidingly abut a stationary conduitfor the centrifugal drum. By employing a thin sealing lip as the onlyabutting connecting surface, the wear is decreased since an edge isemployed having minimal sliding contact area. By employing such sealingsleeves having a thin sealing lip in the form of rubber, flexibleplasticor other material, the elasticity of the connection is increased.

Constructions have also been proposed whereby the with this arrangement.

3,126,338 Patented Mar. 24, 1964 ice stationary inlet and outlet lineswhich flow-connect with sealing sleeves of the foregoing type are formedof flexible or elastic material or include a flexible or elastic portiontherealong so that such stationary lines will yield in consequence ofvarying lateral pressure caused by the radial oscillations of the drumout of the normal path. Therefore the pressure which would otherwise beexerted fully against the sealing sleeves by the drum parts is taken upto some extent by the elastic or flexible inlet and outlet lineconstruction. With respect to slight radial oscillations out of thenormal path of rotation wherein only a slight deflection or movement ofthe elastically or flexibly arranged inlet and outlet lines is required,the pressure transmitted by the sealing sleeve connected therewith iscorrespondingly slight so that thedesired function is achieved On theother hand, however, greater oscillations of the centrifugal drum out ofits normal path, i.e., wherein a greater amplitude of radial movement isencountered, would require a correspondingly greater deflection ormovement such that the forces to be transmitted by the sealing sleeveswould be correspondingly greater. Accordingly, considerable wear andtear will occur with respect to the sealing sleeves since such greaterforces are not readily transmitted to the flexibly connected stationaryinlet and outlet lines.

Particularly large amplitude oscillations of the drum out of its normalaxial path will occur where solids separated from a carrier liquid areejected from the drum at specific time intervals. This is normallycarried out using a drum separator, for example, having peripheraldischarge openings therein which are closed during the separatingoperation and then opened for discharging the collected solids. Thesudden opening of the discharge openings to effect the emptying of thesolids from the drum and the irregular emergence of the solids throughthe discharge openings result in imbalances. These cause strong andviolent shaking of the rotating drum and consequently lead to radialoscillations of the drum out of its normal rotational path and strongwear and tear on the seals. Moreover, with respect to marine centrifugaldrum arrangements, because of the rocking and rolling of the ship,relative movements of considerable extent occur between the rotating andstationary parts of the centrifugal drum arrangement leading to similarproblems of wear and tear. This is particularly true at the outermostpositions of the drum axis with respect to the normal axis of rotation,i.e., at the point where the ocsillating direction reverses from oneside to the other.

For the aforementioned reasons, it has not been possible in the past touse effectively self-discharging or automatically discharging sludgeseparators and marine separators of the heremeticaly sealed type.

It is an object of the present invention to overcome the foregoingdrawbacks and to provide a hermetically sealable radially displaceablemounting means for a centrifugal drum whereby the mounting means may bedisplaced together with the drum out of the normal position so that noundue pressure will be exerted on the packing or seal between thestationary and rotating parts of the drum arrangement.

Other and further objectives will become apparent from a study of thewithin specification and accompanying drawing, in which FIGURE 1 is aschematic side elevational view partly in section of a centrifugal drumarrangement in accordance with the invention, and

found that a hermetically scalable mounting arrangement may be providedfor a centrifugal drum having inlet means and outlet means for thematerial treated within the drum, which comprises mounting means forrotatably receiving the drum, said mounting means being positioned foroscillatory displacement together with the drum out of the normalrotational path of the drum. The mounting means includes chamber meansfor outwardly enclosing the drum inlet and outlet means for the materialtreated in the drum in hermetically sealed, rotatable condition, thechamber means being adapted for flow connecting the inlet and outletmeans with an inlet source and outlet recovery means, respectively, forthe material treated within the drum.

The mounting means is normally rotationally stationary and thearrangement is provided with means for rotating the drum within themounting means with the inlet and outlet means of the drum inhermetically sealed condition. In this manner the mounting means may belimitedly radially displaced as a unit together with the drum out of thenormal position.

Preferably the mounting means includes bearing means for rotatablyreceiving the drive shaft of the centrifugal drum and a casing enclosingthe bearing means having a removable hood or cover portion forpermitting access to the interior of the casing.

The chamber means includes at least one inlet-sourceconnectable inletchamber flow connected with the drum inlet means and at least oneoutlet-recovery-means-connectable outlet chamber flow connected with thedrum outlet means. The portions of each said chamber connected with thedrum inlet and outlet means are preferably defined as resilient annularsurfaces or edges adapted to slidably contacting the correspondingportions of the drum inlet and outlet means in rotational sealingabutment therewith.

In accordance with the preferred embodiment of the invention, the druminlet means is flow connected to an inlet source for the materialtreated within the drum through the inlet chamber, and the drum outletmeans is flow connected to an outlet recovery means for said materialthrough the outlet chamber, by flexible conduit means, respectively.

In accordance with one embodiment of the invention wherein thecentrifugal drum is equipped with peripheral discharge openings thereinfor the removal of solids material separately from a liquid carriertherefor, for example a conventional sludge discharge drum separatorhaving automatic means for opening and closing the discharge openings,the cover means is additionally provided with peripheral dischargeconduit means for conducting away material peripherally discharged fromthe drum through the peripheral discharge openings or ports.

Thus, a hermetically sealed centrifugal drum arrangement is provided inaccordance with the present invention wherein a centrifugal drum havingdrum inlet and outlet means for material treated therewithin is providedwith mounting means for rotatably receiving the drum, said mountingmeans being positioned for displacement together with the drum out ofthe normal rotational path of the drum. The mounting means specificallyinclude support means or bearing means for rotatably receiving the drumand cover means or casing for enclosing the drum and support means.Advantageously, the support means and cover means are both mounted forradial oscillatory displacement together with the drum out of the normalposition thereof, such that the chamber means forming a part of thecover means which outwardly encloses the drum inlet and outlet means inhermetically sealed condition will also be displaced in like manner. Asa result, no wear and tear will take place between the rotating inletand outlet parts of the drum and the chamber means operatively connectedthereto, since all of these parts will be simultaneously radiallydisplaced as the drum is subjected to radial displacement. Due to theprovision for flexible connections between the inlet source and outletrecovery means, on the one hand, and

the chamber means on the other, any radial displacement will be taken upand not transmitted to the stationary inlet source and outlet recoverymeans, respectively.

In accordance with the invention, therefore, a centrifugal drum isprovided in which even very great amplitudes of oscillation andcorresponding radial displacement of the centrifugal drum may beaccommodated without unfavorably influencing the packing or seal betweenthe ro tating and stationary parts of the drum arrangement for feedingand withdrawing flowable materials treated within the drum. In thismanner, the major cause for accelerated wear and tear of the packings orseals between the rotating and stationary parts of the drum arrangementis avoided and only the normal wear and tear of such parts will occurindependently of the movements of the centrifugal drum out of its normalrotational path.

Referring to FIGURE 1 of the drawing, a centrifugal drum 9 is arrangedwithin a frame 1 such that its shaft 3 is operatively connected to thedrive wheel 2 of any conventional drive means (not shown). The drum 9 ispositioned within a cover 7 which generally encloses the drum. The shaft3 is mounted for rotation within the lower portion of cover or casing 7by means of upper radial bearing 4, lower radial bearing 5 as well asend bearing 6, so that shaft 3 may be rotated by means of drive wheel 2operatively connected with gear 2' of shaft 3. The lower portion ofcover or casing 7 is positioned on resilient mounting surface 1" whichmay be formed of rubber or other suitable shock-absorbing materialpositioned on frame 1 while the intermediate portion of cover 7 adjacentto the upper portion of shaft 3 is connected to frame 1 by means of aplurality of circumferential resiliently mounted neck bearings 8 whichserve to dampen the simultaneous radial oscillations of cover 7 anddrum 1. It will be appreciated in this manner that as drum 9 issubjected to radial displacement with respect to its normal axis ofrotation, the cover 7 within which shaft 3 is mounted will also beradially displaced in the same manner. Generally, a pendulum movement oroscillation of the drum 9, shaft 3 and cover 7 will take place about themid-point of surface 1" as pivot point which will be dampened by neckbearings 8.

Attached to the upper portion of stationary cover 7 is a removable hood10 also stationarily positioned with respect to the rotating drum. Theupper portion of hood 10 is constructed as a chamber means 10 forenclosing the inlet and outlet means of the drum in hermetically sealedcondition.

The upper portion of drum 9 is provided with a neck portion 17 includingthree concentric flow pipes. The outermost flow pipe of neck portion 17terminates within lower outlet chamber 16', the intermediate flow pipeterminates within upper outlet chamber 15, while the innermost flow pipeterminates within inlet chamber 17 An annular outlet flow conduit 16"passes from the drum interior between the outermost and intermediateflow pipes and communicates in hermetically sealed condition with loweroutlet chamber 16' and, in turn, with outlet recovery pipe 16 havinginterposed therealong a flexible pipe portion 20 capable ofaccommodating axial movement of pipe 16. Flow conduit 16 serves toremove a heavier liquid fraction from the drum separately from a lighterliquid fraction and solids content of the material being treated in thedrum.

In the same way, an annular outlet flow conduit 15" passes from the druminterior between the intermediate and innermost flow pipes andcommunicates in hermetically sealed condition with upper outlet chamber15' and, in turn, with outlet recovery pipe 15 having interposedtherealong a flexible pipe portion 19 for the same purpose as flexiblepipe portion 20. Flow conduit 15" serves to remove from the drum alighter liquid fraction separately from the heavier liquid fractionremoved through flow conduit 16".

The innermost flow pipe extends through the lower outlet chamber 16 andthe uppermost outlet chamber and terminates within inlet chamber 1'7 soas to communicate in hermetically sealed condition flexible inletconduit 18, inlet pipe 14 and inlet chamber 17' with the interior of thedrum by means of the flow conduit 17 the innermost flow pipe of neckportion 17. Flexible inlet conduit 18 serves the same purpose for theinlet arrangement as flexible portions 19 and serve for the outletarrangements. The material to be treated in the drum, therefore, maycomprise a sludge material including a mixture of a lighter and aheavier liquid fraction as well as solids material suspended in theliquid.

An annular resilient seal 13, such as a rubber seal, is interposedbetween the lower adjacent portion or lower outlet chamber 16 and theoutermost concentric pipe of neck portion 17 so as to form a connectionbetween the adjacent rotating portion of drum 9 and the stationaryportion of chamber means 10 thereat. In like manner, a seal 12 is*mterposed between the lower adjacent portion of upper outlet chamber 15and the intermediate concentric pipe of neck portion 17 so as to form aconnection between the adjacent rotating portion of drum 9 and thestationary portion of chamber means 10" therea-t. A similar seal 11 isinterposed between inlet chamber 17' and the innermost concentric pipeof neck portion 17 so as to form a connection between the adjacentrotating portion of drum 9 and the stationary portion of chamber means10 thereat. In this connection, the chamber means 10' includes thehousing portion of hood 1% which encloses chambers 16, 15' and 17' whichform the connection between the stationary parts of the hermeticallyscalable chamber means and the rotating parts of the drum therewithin.

Centrifugal drum 9 is provided in this embodiment as a sludge dischargeseparating drum having a plurality of spaced apart openings or ports 9"defined along its periphery at a level intermediate the upper and lowerends of the drum. At the level of ports 9 an annular opening 23' withinterposed ribs is provided along the periphery of cover 7. Frame 1 inturn includes a trough chamber 23 outwardly of and peripherallyenclosing the portion of cover 7 provided with opening 23. A suitabledischarge conduit 23" flow communicates trough chamber 23 withcollecting means (not shown) for recovering the sludge fractionseparated within the drum. in order topermit radial movement ct" hood 10in relation to frame 1, resilient rings or strips 24 interconnect theupper and lower edges of the peripheral portion of cover 7 containingopening 23 with the adjacent edges of trough chamber 26.

For control of the opening and closing of sludge discharge ports 9 ofdrum 9, any conventional means may be provided, such as a slidablepiston having an annular ring portion axially movable from a positionclosing to a position opening ports 9 and vice versa. Such constructionsare well known, and commonly use a control liquid, such as water, whichin this case continuously passes through flexible conduit 22 (whichserves the same purpose as flexible portions 18, 19 and 21)), pipe 21and nozzle 21' into a lower annular recess 9 in drum 9. Due to thecentrifugal motion of drum 9, the liquid received within recess 9" willpass into the drum via control inlet 9". Such liquid serves to displacethe piston within the drum to close the ports 9'. After interruption ofthe liquid feed, the ports 9 are opened under the pressure of thebowl-fillings (as is known). It will be appreciated in this respect thatwhen the control liquid is allowed to pass through nozzle 21, the samewill enter drum 9 and displace the slidable piston to axially move theannular ring portion from a position normally opening to a positionclosing the ports 9. Upon termination of the flow of the control liquidthrough nozzle 21, the control liquid within the drum will flow outthrough suitable exit ports so that the piston return to the 6 aposition normally opening ports 9". Any control liquid which may be lostin the vicinity of recess 9" will be prevented by shield 21" frompermeating the lower drum parts, including shafit 3, bearings 4, etc.,and such control liquid will leave by means of exit ports 7 and 1'.

It will be appreciated that with respect to stationary frame 1, cover 7including hood 1t} and chamber means 10 will execute pendulum movementsor radial displacements from the normal axis of rotation together withdrum 9, shaft 3 and neck portion 17 Without any load being placed on theresilient seals 11, 12 and 13 other than the normal load present by dintof the sliding contact between the moving parts, i.e., the concentricflow pipes of neck portion 17, and the stationary parts, i.e., chambers16, 15' and 17, connected to the pipes of neck portion 17 by means ofsaid resilient seals 11, 12 and 13. Any pendulum movements or radialdisplacement will be radially taken up by the flexible portions 18, 1-9and 2G, neck bearings 8, as well as the surface 1" which serves as abase pivot point for the entire mounting on frame 1.

Thus, a construction is provided in accordance with the inventionwherein the drum 9 and inlet and outlet means, including neck portion17, on the one hand, and the chamber means for flow connecting saidinlet and outlet means with the drum exterior in hermetically sealedcondition, on the other hand, are unable to execute any relativemovements with respect to one another other than the rotational movementof the drum parts.

In FIGURE 2 a similar embodiment of the hermetically sealed chambermeans in accordance with the invention is shown in enlarged detail. Drumis provided with conventional outlet flow conduits 150" and outlet flowconduits 150" for the specifically heavier liquid fraction and lighterliquid fraction, respectively, passing out from the drum interior. Flowconduits 16%" are spaced about the periphery of the drum Wall andcommunicate with lower outlet chamber 160', while flow conduits 150"pass from the drum interior to upper outlet chamber 150'. An axial inletflow conduit 17h" flow communicates inlet chamber 17% with the interiorof the drum for feeding the materials to be treated into the drum, Thelower connection between outlet chamber 160' and the neck portion 176,which includes outlet flow conduits 160 and 15% as well as inlet flowconduit 170", is provided by annular resilient seal 130. In the samemanner, annular resilient seals are provided as the upper connection ofchamber 160' and as the lower connection of chamber 150, respectively.Annular resilient seals 110 are provided as the upper connection ofchamber 15th and as the lower connection of chamber 170', respectively.Chamber 160 flow communicates with outlet recovery pipe 160 havinginterposed therealong a flexible pipe portion 200 capable ofaccommodating axial movement of pipe 160. In the same Way, chamber 159'flow communicates with outlet recovery pipe 150 having interposedtherealong a flexible pipe portion 190 capable of accommodating axialmovement of pipe 150. Flexible inlet conduit 18h interposed in the inletconduit flow communicates inlet pipe and inlet chamber 170' with theinterior of the drum via flow conduit 17%". The function and arrangementof the foregoing parts are similar to those of the corresponding partsin FIGURE 1.

The chamber means 160, which includes in hermetically sealed conditionthe inlet and outlet conduits for drum 90, is positioned upon hood 100which is releasably connected to cover 70 by spring loaded latches 70'.It will be seen that chamber 160 is defined by annular element ltitlaand annular element 160a situated in pressing engagement upon the upperportion of hood 100. Chamber 1513 is defined by annular element a andannular element 170a situated in pressing engagement upon the upperportion of annular element a. Chamber is defined by annular element 140asituated in pressing engagement upon annular element 150a. Theparticular annular elements making up the chamber means 100' aremaintained in stacked relationship in pressing engagement one upon thenext by means of lever 30 and coacting spindle 31 pressing against cover33 of annular element 140a. Lever 30 and spindle 31 are positioned onbracket 32 secured to hood 100 by bolt 34.

The chamber means 100, therefore, will efficiently maintain the inletand outlet flow conduits of the drum in hermetically sealed condition sothat the material to be treated in the drum may be passed therethroughvia flexible portion 180 and the liquid material already treated in thedrum may be passed therefrom via flexible portions 190 and 200. In thesame manner as carried out in accordance with the construction of FIGURE1, the chamber means 100', hood 100 and cover 70 will be radiallydisplaced together with drum 90 and neck portion 170 out of the normalpath of rotation. It will be appreciated that any leakage which mayoccur in the normal centrifugal operations at the seals 110, 120 and130, as is known, will be carried off by means of conventional run-offgrooves 101, 102, 103, 104 and 105.

What is claimed is:

1. Hermetically sealable centrifugal drum arrangement which comprises acentrifugal drum having at the top end portion thereof drum inlet meansand outlet means for the material treated within the drum, mountingmeans rotatably receiving and completely enclosing the drum, stationarybase means, said mounting means being pivotally positioned on said basemeans for displacement together with the drum out of the normalrotational path of the drum and including chamber means outwardlyresiliently enclosing in hermetically sealed rotatable condition thedrum inlet and outlet means for the material treated in the drum, inletsource flexible conduit means and outlet recovery flexible conduitmeans, said chamber means flow communicating said inlet and outlet meanswith said inlet source and outlet recovery means, respectively, for thematerial treated within the drum, and said chamber means beingdisplaceable together with the drum inlet and outlet means out of saidnormal path.

2. Drum arrangement according to claim 1 wherein said mounting means arerotationally stationary yet mounted on said base means for limitedoscillatory displacement together with the drum out of normal position.

3. Drum arrangement according to claim 2 wherein said chamber meansincludes at least one inlet chamber flow connecting said inlet sourcemeans with the drum inlet means and at least one outlet chamber flowconnecting said outlet recovery means with the drum outlet means.

4. Drum arrangement according to claim 3 wherein the correspondingportions of said chambers connected with the drum inlet and outlet meansare defined as resilient annular surfaces adapted to slidably contactthe corresponding portions of said drum inlet and outlet means inrotational sealing abutment therewith.

5. Drum arrangement according to claim 4 wherein said drum is providedwith a drive shaft, said mounting means include bearing means forrotatably receiving the drive shaft of the centrifugal drum and a casingenclosing said bearing means and the drum, said casing having a emovablehood portion for permitting access to the interior of the casing, saidchamber means being positioned on said hood portion, and said bearingmeans, casing, hood portion and chamber means being mounted resilientlyon said base means for limited oscillatory displacement together withthe drum out of normal position.

6. Drum arrangement according to claim 5 wherein said drum is providedwith peripheral drum discharge ports and said casing is additionallyprovided with hermetically sealed peripheral discharge conduit means,for conducting away material peripherally discharged from the drumthrough said peripheral drum discharge ports.

7. In a centrifugal drum arrangement, including a centrifugal drummounted for rotation and having inlet and outlet means rotatabletherewith and stationary inlet source means and outlet recovery means,respectively, for the material treated in the drum, the improvementwhich comprises mounting means rotatably receiving and completelyenclosing the drum, stationary base means, said mounting means beingpositioned resiliently pivotally on said base means for oscillatorydisplacement together with the centrifugal drum, and said mounting meansincluding chamber means outwardly resiliently enclosing the drum inletand outlet means in hermetically sealed rotatable condition, andflexible conduit means, said chamber means hermetically sealably flowcommunicating said inlet and outlet means by said flexible conduit meanswith said inlet source and outlet recovery means, respectively, for thematerial treated in the drum, said chamber means being displaceabletogether with the drum inlet and outlet means out of the normalrotational path of the drum.

References Cited in the file of this patent UNITED STATES PATENTS2,043,350 Forsberg June 9, 1936 2,358,779 Tholl Sept. 26, 1944 2,461,674Aronson Feb. 15, 1949 2,575,689 Smith Nov. 20, 1951 2,916,201 Hemfort etal. Dec. 8, 1959 3,026,701 Houser Mar. 27, 1962 3,040,899 Kron June 26,1962 3,061,181 Gooch Oct. 30, 1962 FOREIGN PATENTS 630,307 Germany May25, 1936

1. HERMETICALLY SEALABLE CENTRIFUGAL DRUM ARRANGEMENT WHICH COMPRISES ACENTRIFUGAL DRUM HAVING AT THE TOP END PORTION THEREOF DRUM INLET MEANSAND OUTLET MEANS FOR THEMATERIAL TREATED WITHIN THE DRUM, MOUNTING MEANSROTATABLY RECEIVING AND COMPLETELY ENCLOSING THE DRUM, STATIONARY BASEMEANS, SAID MOUNTING MEANS BEING PIVOTALLY POSITIONED ON SAID BASE MEANSFOR DISPLACEMENT TOGETHER WITH THE DRUM OUT OF THE NORMAL ROTATIONALPATH OF THE DRUM AND INCLUDING CHAMBER MEANS OUTWARDLY RESILIENTLYENCLOSING IN HERMETICALLY SEALED ROTATABLE CONDITION THE DRUM INLET ANDOUTLET MEANS FOR THE MATERIAL TREATED IN THE DRUM, INLET SOURCE FLEXIBLECONDUIT MEANS AND OUTLET RECOVERY FLEXIBLE CONDUIT MEANS, SAID CHAMBERMEANS FLOW COMMUNICATING SAID INLET AND OUTLET MEANS WITH SAID INLETSOURCE AND OUTLET RECOVERY MEANS, RESPECTIVELY, FOR THE MATERIAL TREATEDWITHIN THE DRUM, AND SAID CHAMBER MEANS BEING DISPLACEABLE TOGETHER WITHTHE DRUM INLET AND OUTLET MEANS OUT OF SAID NORMAL PATH.